Simon Kim Gang-i, also called ‘Yeosaeng`, was born in Seosan, Chungcheong-do to a middle class family and became a Catholic as an adult. He was both noble and brave, as well as being rich. When he became a Catholic, he left his hometown, giving up his wealth and servants, and went to Gosan, Jeolla-do to live with the family of his brother Thaddeus Kim Chang-gwi.

When Father James Zhou Wen-mo went on pastoral visitation Gosan, in the early summer of 1795, Simon Kim visited him many times to receive the Sacraments and learn the catechism. During the Shinyu Persecution in 1801, he was sought by the police, so he had to hide by going from place to place for one year.

Meanwhile, his wife was arrested by the police and imprisoned for one year. She was released after she payed a big sum of money to the police. When the persecution was over, Simon Kim became a peddler and dedicated himself to proclaiming the Gospel. When he realized that a peddler`s life was not helpful to his faith life, he gave it up and went to Meorusan in Jinbo, Gyeongsang-do (now, Posan-dong, Seokpo-myeon, Yeongyang-gun, Gyeongbuk) and formed a Christian village there. Afterwards, he traveled from place to place and finally settled in Uljin, Gangwon-do.

Simon Kim was arrested during the Eulhae Persecution that broke out in 1815, in Gyeongsang-do, with his brother Thaddeus and his nephew Andrew Kim Sa-geon, after being secretly reported by his former servant. They were imprisoned in Andong. Simon Kim bravely went to the chief official and asked him to return his property that had been confiscated. Surprisingly, the chief official accepted his request without argument. As a result Simon Kim was able to dispose of his property and provide food for the faithful in prison, who were suffering from hunger.

Simon Kim was subjected to severe interrogations, while he was in Andong prison, but he stood firm in his faith. Then in May he was transferred to Wonju, Gangwon-do with his brother. There also, he had to go through severe interrogation and torture. His younger brother became so weak that he denied his religion. However, Simon Kim did not succumb under any punishment.

The great faith and endurance which Simon Kim professed, moved everybody. Then the governor, on realizing that it was impossible to make him surrender, pronounced the death sentence on him and reported it to the royal court asking for the king`s approval of his execution. The report reads as follows:

"Kim Gang-i secretly propagated this religion and distributed Catholic books. He studied Catholic doctrine for years and was deeply involved in that religion. Thus, I beseech you to allow me to execute the law, accordingly."

The king immediately approved the pronouncement of the death sentence and gave permission to carry it out. At that time, however, Simon Kim was completely exhausted and suffered terribly from the wounds of torture. In addition, he could not move even a finger because of dysentery, which he had contracted while in the prison. As a result, he died in prison before the king`s order reached the governor. It was on December 5, 1815 (November 5, by the Lunar calendar). Simon Kim was over 50 years old.